Fuel injection valve

ABSTRACT

A fuel injector, in particular for direct injection of fuel into a combustion chamber of an internal combustion engine, having an actuator for actuating a valve needle, the valve needle having on one injection end a valve-closure member which forms a sealing seat together with a valve-seat surface formed on a valve-seat member. Fuel channels are provided in a valve needle guide which is designed in one piece with or is connected to the valve-seat member and they open into a swirl chamber. The number of fuel channels is such that a turbulent flow produced in the swirl chamber is homogeneous in a circumferential direction.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

German Published Patent Application No. 196 25 059 describes a fuelinjector having multiple fuel channels in a flow path of the fuel from afuel inlet to an injection orifice, the cross section of the channelsdetermining the amount of fuel injected per unit of time at a given fuelpressure. To influence the fuel distribution in a fuel cloud injected,at least some of the fuel channels are oriented so that the streams offuel coming out of them are injected directly through the injectionorifice.

One disadvantage of the fuel injector known from the publication citedabove is in particular the fact that the fuel channels are situated in aplane perpendicular to the direction of flow of the fuel, i.e., theorifices are situated on a circle around a valve needle guide connectedto the valve-seat member. In this way, the quantity of fuel flowingthrough the fuel injector is not metered accurately enough when thevalve-closure member is lifted up from the sealing seat.

Furthermore, the number of bores is not sufficient to produce asufficiently homogenous fuel cloud which meets stoichiometricrequirements for complete combustion. This is further reinforced by thelarge diameter of the fuel channels.

SUMMARY OF THE INVENTION

The fuel injector according to the present invention has the advantageover the related art that a turbulent flow created by the fuel flowingthrough the fuel channels into the swirl chamber remains homogenous inthe circumferential direction without any compensatory measures, thevolume of the swirl chamber being so small that it is possible tomaintain the turbulent flow even during the dead time of the fuelinjector.

It is advantageous in particular that the large number of fuel channelsensures a very homogeneous cloud of mixture.

The fuel channels are advantageously formed in a hollow cylindricalvalve needle guide which is either designed in one piece with thevalve-seat member or is connected to it so that eccentricity and tiltingof the valve needle are prevented.

The design of the fuel channels in an annular insert which is insertableinto the valve-seat member is especially simple to manufacture and maybe used for any desired designs of fuel injectors, because thevalve-seat member need only have a cylindrical recess to accommodate theinsert.

The shape of the swirl chamber, which is designed as a recess on theinjection side of the insert, is also advantageous. Any desired volumemay be obtained by appropriate lathing or similar machining and adaptedto requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic section through an embodiment of a fuelinjector according to the related art.

FIG. 2A shows a schematic section through a first embodiment of a fuelinjector according to the present invention in area IIA in FIG. 1.

FIG. 2B shows a schematic section through the first embodimentillustrated in FIG. 2A along line IIB—IIB in FIG. 2A.

FIG. 3A shows a schematic section through a second embodiment of a fuelinjector according to the present invention in area IIA in FIG. 1.

FIG. 3B shows a schematic section through the second embodimentillustrated in FIG. 3A along line IIB—IIB in FIG. 3A.

FIG. 3C shows a schematic section along line IIIC—IIIC in FIG. 3A.

FIG. 4A shows a schematic section through a third embodiment of a fuelinjector according to the present invention in area IIA in FIG. 1.

FIG. 4B shows a top view of the third embodiment of the fuel injectoraccording to the present invention as illustrated in FIG. 4A.

DETAILED DESCRIPTION

Before describing embodiments of a fuel injector 1 according to thepresent invention in greater detail on the basis of FIGS. 2 through 4, aknown fuel injector 1 of the same design will first be explained brieflywith respect to its advantageous components on the basis of FIG. 1,except for the measures according to the present invention for theseembodiments, to permit a better understanding of the present invention.

Fuel injector 1 is designed in the form of a fuel injector for fuelinjection systems of internal combustion engines having compression of afuel mixture and spark ignition. Fuel injector 1 is suitable inparticular for direct injection of fuel into a combustion chamber (notshown) of an engine.

Fuel injector 1 has a nozzle body 2 in which a valve needle 3 issituated. Valve needle 3 is mechanically linked to a valve-closuremember 4 which cooperates with a valve-seat surface 6 situated on avalve-seat member 5 to form a sealing seat. Fuel injector 1 in thisembodiment is an inwardly opening fuel injector 1 having an injectionorifice 7. Nozzle body 2 is sealed with respect to stationary pole 9 ofa solenoid 10 using a gasket 8. Solenoid 10 is encapsulated in a coilcasing 11 and wound onto a field frame 12 which is in contact with aninternal pole 13 of solenoid 10. Internal pole 13 and stationary pole 9are separated by a gap 26 and are supported on a connecting part 29.Solenoid 10 is energized by an electric current supplied via an electricplug contact 17 over a line 19. Plug contact 17 is surrounded by plasticsheathing 18 which may be integrally extruded onto internal pole 13.

Valve needle 3 is guided in a valve needle guide 14 designed in theshape of a disk. A matching adjustment disk 15 is used to adjust thelift. An armature 20 is situated on the other side of adjustment disk15. The armature is connected in a friction-locked manner to valveneedle 3, which is in turn connected by a weld 22 to first flange 21. Arestoring spring 23, which in the present design of fuel injector 1 isprestressed by a sleeve 24, is supported on first flange 21.

A second flange 31 which is connected to valve needle 3 by a weld 33functions as a lower armature stop. An elastic intermediate ring 32which sits on second flange 31 prevents rebound when fuel injector 1closes.

Fuel channels 30 a to 30 c, which carry the fuel supplied through acentral fuel feed 16 and filtered through a filter element 25 toinjection orifice 7, run in a valve needle guide 14, in armature 20 andon valve-seat member 5. Fuel injector 1 is sealed by a gasket 28 withrespect to a fuel line (not shown here).

In the resting state of fuel injector 1, armature 20 is acted upon byrestoring spring 23 against its direction of lift, so that valve-closuremember 4 is held in sealing contact on valve seat 6. When solenoid 10 isenergized, it creates a magnetic field which moves armature 20 in thedirection against the elastic force of restoring spring 23, the liftbeing predetermined by a working gap 27 in the resting position betweeninternal pole 12 and armature 20. Armature 20 also entrains flange 21,which is welded to valve needle 3, in the direction of lift.Valve-closure member 4, which is mechanically linked to valve needle 3,is lifted up from valve-seat surface 6 and the fuel directed atinjection orifice 7 through fuel channels 30 a through 30 c is injected.

When the coil current is disconnected, armature 20 drops away frominternal pole 13 due to the pressure of restoring spring 23 after themagnetic field has been reduced sufficiently, so that flange 21, whichis mechanically linked to valve needle 3, moves against the direction oflift. Valve needle 3 is therefore moved in the same direction, so thatvalve-closure member 4 comes to rest against valve-seat surface 6 andfuel injector 1 is closed.

In a detail of a sectional diagram, FIG. 2A illustrates a firstembodiment of a fuel injector 1 according to the present invention. Thedetail shown here is labeled as IIA in FIG. 1.

The part of fuel injector 1 on the injection side, illustrated in FIG.2A, has nozzle body 2 with valve-seat member 5 inserted into it. Atleast one injection orifice 7 is formed in valve-seat member 5.Valve-seat member 5 is connected to nozzle body 2 by a weld 45.

Valve-seat member 5 has a first annular recess 41 into which an annularinsert 40 is inserted. Fuel channels 35 are formed in annular insert 40.In the present first embodiment, fuel channels 45 are arranged in tworows 34 forming concentric rings. Fuel channels 35 may be arranged insuccession radially or with a mutual circumferential offset.

At the outflow end of first annular recess 41, there is a second annularrecess 42 forming a swirl chamber 43. Fuel channels 35 in annular insert40 open into swirl chamber 43. They thus extend from an inlet end faceof valve-seat member 5 in which first annular recess 1 is formed toswirl chamber 43.

To obtain the required accuracy in metering fuel, fuel channels 35should have a very small diameter, e.g., less than 100 μm, in particular70 μm. Such small-caliber bores may be produced by laser machining, forexample.

Fuel channels 35 are inclined at an angle α in the injection directionwith respect to a plane running parallel to inlet end face 44 ofvalve-seat member 5. Angle of inclination a may be achieved, forexample, by an appropriate adjustment of the axial diameter of annularinsert 40. To impart turbulence to fuel flowing through fuel channel 35,fuel channels 35 have a tangential component relative to center axis 37of fuel injector 1. After flowing through fuel channels 35, fuelcollects in swirl chamber 43, producing a turbulent flow in acircumferential direction. The greater the number of fuel channels 35provided, the more homogeneous may be the turbulent flow and the lowerthe loss occurring in the dead time of fuel injector 1 between twoinjection cycles. As soon as valve needle 3 is lifted up from thesealing seat in the direction of lift, the fuel having turbulenceimparted to it may be injected through injection orifice 7 into the fuelchamber (not shown) of an internal combustion engine.

FIG. 2B shows a schematic sectional view through the first embodiment ofa fuel injector 1 according to the present invention, as shown in FIG.2A, along line IIB—IIB in FIG. 2A. In the embodiment illustrated in FIG.2B, fuel channels 35 are arranged in two rows 34, with a mutual offsetin a circumferential direction. Fuel channels 35 have a very smalldiameter, e.g., between 100 μm and 70 μm. Number n of fuel channels 35is limited only by the stability requirement. This means that a web,which is at least as wide as the diameter of the fuel channels, remainsbetween two adjacent fuel channels 35. It is advantageous for at leastten fuel channels 35 to be provided, even more advantageous for at least50 fuel channels to be provided, and yet more advantageous for at least100 fuel channels to be provided.

FIG. 3A shows a schematic section through a second embodiment of a fuelinjector 1 according to the present invention, likewise in area IIA inFIG. 1.

In the embodiment in FIG. 3A, valve seat carrier 5 has a hollowcylindrical valve needle guide 31, which is either designed in one piecewith valve-seat member 5 or is joined to it, e.g., by soldering, weldingor similar methods. Valve needle guide 31 has fuel channels 35 whichextend from a radially outer side 36 of valve needle guide 31 to aradially inner side of a valve needle guide 31. Fuel channels 35 arearranged in several rows 34. In the present second embodiment, four rows34 are provided. Valve-closure member 4 is guided in valve needle guide31. It is in contact with an inside wall 38 of valve needle guide 31with at least one peripheral guide line 33, valve-closure member 4 beingspherical in the present embodiment.

On actuation of fuel injector 1, fuel flows from radially outer side 36of valve needle guide 31 through fuel channels 35 to radially inner side39 of valve needle guide 31 and from there through the sealing seat intoinjection orifice 7. Fuel channels 35 are preferably aligned in parallelwith a plane defined by guiding line 33, for example. A swirl chamber 43is formed between valve-closure member 4, inside wall 38 of valve needleguide 31 and valve-seat surface 6. This swirl chamber may be designed,for example, in the form of a spherical shell to reduce the volume ofswirl chamber 43.

On actuation of fuel injector 1, fuel flowing through fuel channels 35in the direction of injection orifice 7 produces a turbulent flow inswirl chamber 43. A largely homogeneous turbulent flow develops due tothe large number of fuel channels 35 which are arranged in at least fourrows 34, and this homogeneous turbulent flow is maintained even duringthe dead time of fuel injector 1 between two injection cycles.

FIG. 3B shows a schematic section along line IIB—IIB in FIG. 3A throughthe second embodiment of a fuel injector 1 according to the presentinvention as illustrated in FIG. 3A.

The sectional plane in FIG. 3A is situated along a row 34 of fuelchannels 35. In FIG. 3B, four fuel channels 35 are shown in the firstand third quadrants as representative of all fuel channels 35 which arearranged circumferentially in four rows in valve needle guide 31. Toproduce turbulence, fuel channels 35 are in turn provided with atangential component relative to a center line 37 of fuel injector 1.Fuel channels 35 open into swirl chamber 43 on the radially inner side39 of valve needle guide 31. Due to the large number of fuel channels35, a mostly homogeneous turbulent flow in the circumferential directionis produced also in the present second embodiment.

FIG. 3C shows a schematic section along line IIIC—IIIC in FIG. 3A. Asmentioned above, fuel channels 35 have a tangential component relativeto center line 37 of fuel injector 1 to produce turbulence, so the crosssection of fuel channel 35 in FIG. 3C appears oval. The orientation ofthe tangential components of fuel channels 35 is in the same directionin each row 34 relative to the other rows 34.

FIG. 4A shows a schematic section through a third embodiment of a fuelinjector 1 according to the present invention, likewise in area IIA inFIG. 1.

The present embodiment corresponds in its advantageous components to thefirst embodiment illustrated in FIG. 2A. In contrast with the latter,annular insert 40 in first recess 41, which is formed in inlet end face44 of valve-seat member 5, has only one row 34 of fuel channels 35arranged on the circumference. As in the first embodiment, they areinclined at an angle α to a plane defined by inlet end face 44 ofvalve-seat member 5. Fuel channels 35 open into swirl chamber 43, whichis formed by second recess 42 in valve-seat member 5. In contrast withthe first embodiment, fuel channels 35 have a larger diameter to takeinto account the reduced number of fuel channels 35. The amount of fuelflowing through the channels is the same in each case, so the product ofthe cross-sectional area and the number of fuel channels 35 is also thesame.

FIG. 4B shows a top view of the third embodiment of a fuel injector 1according to the present invention as illustrated in FIG. 4A. Hereagain, individual fuel channels 35 are shown in annular insert 40 asrepresentative. They also have a tangential component relative to centerline 37 of the fuel injector to produce a turbulent flow. As indicatedin FIG. 4B, fuel channels 35 are inclined at an angle α to the planedefined by inlet end face 44 of valve-seat member 45.

All the embodiments described above have in common the fact that theyhave a large number n of fuel channels 35. This number n is at least tenbut is advantageously much larger, amounting to 50 or even 100 or more,for example. The large number n of fuel channels 35 has severaladvantages: first, due to large number n, no high degree of accuracy isrequired of the diameters of fuel channels 35. Any inaccuracies in themanufacturing process are averaged out again by large number n, becausestatistically there will be just as many larger fuel channels 35 asthere are smaller fuel channels. It is sufficient if a statisticalaverage approaches the desired diameter.

Second, the turbulent flow becomes increasingly more homogeneous due toan increase in the number n of fuel channels 35, whereas localaccumulations of fuel, also known as strands, develop when there are afew fuel channels 35, but this should be avoided in particular in directinjection of fuel into the combustion chamber of an internal combustionengine having compression of a mixture and spark ignition. This is alsopromoted in particular by a large volume of swirl chamber 43 because thefuel present in swirl chamber 43 comes to a standstill during the deadtime of injection valve 1 between two injection cycles, and rotation isinduced again with the next injection cycle. Therefore, too much fuel isinjected at the beginning of the injection cycle, but less fuel or eventoo little fuel is injected thereafter. This is prevented by a smallvolume of the swirl chamber according to the present invention and bythe large number n of fuel channels 35.

The present invention is not limited to the embodiments presented hereand is also applicable, for example, to fuel injectors 1 havingpiezoelectric or magnetostrictive actuators 10 and any desiredarrangements of fuel channels 35 in rows 34.

What is claimed is:
 1. A fuel injector comprising: a valve-seat memberon which is formed a valve-seat surface; a valve needle including on aninjection-side thereof a valve closure member that forms a sealing seatwith the valve seat surface; an actuator for actuating the valve needle;and an annular insert that is one of connected to the valve-seat memberand designed in one piece, the annular insert including fuel channelsthat open into a swirl chamber, wherein the number of fuel channels issuch that a turbulent flow produced in the swirl chamber is homogeneousin a circumferential direction; wherein the fuel channels are situatedin circumferential rows in the annular insert.
 2. The fuel injectoraccording to claim 1, wherein the annular insert is insertable into afirst annular recess of the valve-seat member.
 3. The fuel injectoraccording to claim 2, wherein the first annular recess is formed in aninlet end face of the valve-seat member.
 4. The fuel injector accordingto claim 3, wherein the valve needle passes through the annular insertand is guided by the annular insert.
 5. The fuel injector according toclaim 4, wherein the swirl chamber is formed by a second annular recessof the valve-seat member, the second annular recess having a diameterthat is less than that of the first annular recess.
 6. The fuel injectoraccording to claim 5, wherein the second annular recess is situateddownstream from the first annular recess.
 7. The fuel injector accordingto claim 1, wherein the circumferential rows are arranged concentricallyto one another.
 8. The fuel injector according to claim 1, wherein thefuel channels in the annular insert are inclined with respect to acenter axis of the fuel injector.